I understood your point. Past performance is no guarantee of future results. And I've seen multiple people (including MMM) make that same point in several different places; nor am I relying only on one source for advice. (Though if you're suggesting it has no predictive power for long-term averages, that's ridiculous; it's simply that predictions are not in any way guarantees, nor do they in any way let you time the market.)
But even if you don't buy into the 4% rate, or even if you want to make a more conservative assumption, the math for an estimate still works; just use a different multiplier. And you still shouldn't treat that estimate as a guarantee. Retirement doesn't need to be a binary one-way process, where once you retire if you didn't plan well enough you're doomed. One of the lovely advantages of retiring early is that you're still more than capable of working if you want to, or doing some other kind of work.
Nor should you assume that because you planned for 4% (or 3%, or whatever you like), you should withdraw that much like clockwork every year. You might plan for 4%, but then spend 2.5% because that's what you happened to need. And if the market happens to grow 10% in a year, great, but you shouldn't spend 2.5x as much that year. Whatever you don't spend stays in place, growing your buffer even more for future downsides. If you steal away every unexpected upside, averages stop working, and you'll be more screwed by unexpected downsides rather than just living a little more frugally for a while.
Estimates are just that: estimates. They're useful tools for planning, not guarantees.
Again, see the article I linked about safety margins. You're talking all about all the horrible things that could happen. So, have backup plans, and backup backup plans, and you still can retire before your 60s.
But even if you don't buy into the 4% rate, or even if you want to make a more conservative assumption, the math for an estimate still works; just use a different multiplier. And you still shouldn't treat that estimate as a guarantee. Retirement doesn't need to be a binary one-way process, where once you retire if you didn't plan well enough you're doomed. One of the lovely advantages of retiring early is that you're still more than capable of working if you want to, or doing some other kind of work.
Nor should you assume that because you planned for 4% (or 3%, or whatever you like), you should withdraw that much like clockwork every year. You might plan for 4%, but then spend 2.5% because that's what you happened to need. And if the market happens to grow 10% in a year, great, but you shouldn't spend 2.5x as much that year. Whatever you don't spend stays in place, growing your buffer even more for future downsides. If you steal away every unexpected upside, averages stop working, and you'll be more screwed by unexpected downsides rather than just living a little more frugally for a while.
Estimates are just that: estimates. They're useful tools for planning, not guarantees.
Again, see the article I linked about safety margins. You're talking all about all the horrible things that could happen. So, have backup plans, and backup backup plans, and you still can retire before your 60s.